This invention is in the field of cancer diagnostics and therapeutics. In particular, this invention relates to detection of alterations of wild-type KAI1 gene sequence, KAI1 mRNA and KAI1 protein useful in determining the presence of malignant cancer in a subject or a genetic predisposition to malignancy in a subject. The invention further relates to the use of gene therapy to restore the wild-type KAI1 gene product.
It has been widely accepted that carcinogenesis is a multistep process involving genetic and epigenetic changes that dysregulate molecular control of cell proliferation and differentiation. The genetic changes can include activation of proto-oncogenes and/or the inactivation of tumor suppressor genes that can initiate tumorigenesis as well as lead to the progression of tumors. For example, the tumor suppressor gene p53 may be involved in late stages of colorectal carcinomas (Baker, S. J. et al., (1989) Science, 244: 217-221) and a putative metastasis suppressor gene, nm23, was found down-regulated in metastatic tumors versus nonmetastatic tumors (Steeg, P. S. et al., (1988) J. Natl. Canc. Inst., 80:200-204). In addition, the activation of ras oncogene and the amplification of N-myc have been associated with progression of human tumors such as breast carcinomas (Liu, E. et al., (1988) Oncogene 3:323-327); and neuroblastomas (Brodeur, G. M. et al., (1984) Science, 224:1121-1124; Schwab, M. et al., (1984) Proc. Natl. Acad. Sci. U.S.A., 81:4940-4944) but they are unlikely to be universal determinants of tumor progression (Nicolson, G. L. Bio Essays, 13:337-342 (1991).
However despite these advances in understanding the genetic changes underlying carcinogenesis, metastasis, which is the main cause of death for most cancer patients (Rosenberg, S. A., Surgical Treatment of Metastasis Cancer (Lippincott, Philadelphia Pa. 1987)), remains one of the most important but least understood aspects of cancer (Liotta, L. A. et al. (1991) Cell, 64:327-336; Nicolson, G. L. (1991) BioEssays, 13:337-342 and Steeg, P. S. (1992) Curr. Opin. Oncol., 4:134-141). Accordingly, the isolation of metastasis tumor suppressor genes is of great importance for the diagnosis and therapy of cancers.
Cell fusion studies by Ramshaw et al. ((1983) Int. J. Cancer, 32:471-478) in which hybridization of non-metastatic and metastatic tumor cells produced cell hybrids which are tumorigenic but no longer metastatic demonstrated the existence of metastasis suppressor genes. More recently, Ichikawa et al. (1991) Cancer Res., 51:3788-3792) demonstrated that the metastatic ability of rat prostatic cancer cells was suppressed when fused to non-metastatic cancer cells and that the reexpression of metastasis was associated with the consistent loss of a normal rat chromosome. A subsequent study using micro-cell-mediated chromosome transfer further mapped a putative human metastasis suppressor gene to the 11p11.2-13 region of human chromosome 11. (Ichikawa et al. (1992 Cancer Res., 52:3486-3490) In this study, these researchers demonstrated that a hybrid retaining human chromosome 11cent-p13 showed a suppression of metastasis while hybrids retaining 11cent-p11.2 did not.
In sum, the data presented in the Ichikawa et al. papers suggested that a putative suppressor gene in the p11.2-13 region of human chromosome 11 may play a role in metastasis. However to date, no gene has been identified in this region which is a candidate metastasis suppressor gene. Thus, there is a need in the art to identify such gene(s) in this chromosome region and to determine if any such gene(s) is associated with metastasis.
The present invention relates to methods for detecting alterations of the wild-type KAI1 gene where detection of such alterations is useful in determining the presence of a malignant cancer in a subject or a genetic predisposition to malignancy in a subject. A first method for detecting alterations of the wild-type KAI1 gene comprises analyzing the DNA of a subject for mutations of the KAI1 gene. A second method for detecting alterations of the KAI1 gene comprises analyzing the RNA of a subject for mutations and altered expression of the mRNA product of the KAI1 gene.
The present invention therefore provides nucleic acid probes for detection of alterations of the wild-type KAI1 gene.
The present invention further provides a diagnostic kit containing purified and isolated nucleic acid sequences useful as PCR primers in analyzing RNA or DNA of a subject for alterations of the wild-type KAI1 gene. These PCR primers can also be used to determine the nucleotide sequence of KAI1 alleles.
A third method for detecting alterations of the wild-type KAI1 gene comprises analyzing protein of a subject for alterations in the expression of KAI1 protein.
The invention therefore relates to antibodies to the KAI1 protein and to a diagnostic kit containing antibodies to KAI1 protein useful for detecting alterations in KAI1 protein expression in a subject.
The present invention further provides a method for supplying the wild-type KAI1 gene to a cell having altered expression of the KAI1 protein, the method comprising: introducing a wild-type KAI1 gene into a cell having altered expression of KAI1 protein such that the wild-type gene is expressed in the cell.